1. Field of the Invention
This invention relates generally to devices for receiving and transmitting light to a sample to be analyzed, and more particularly to a probe for use with a device for spectral analysis.
2. Background
There are a number of different devices which are used for rapid, accurate spectral analysis of the reflectivity, transmissivity or transflectance of samples. One of these devices, disclosed in U.S. Pat. No. 4,540,282 to Landa (the Landa patent), is a device which enables immediate and rapid analysis of a number of different products. This type of device can measure three generalized types of information: the chemical constituents of a sample; the physical constituents of a sample; and the quality parameters of a sample.
The chemical constituents of a product include such things as the octane number in gasoline or the amount of aromatics in gasoline. In another environment, such items as the amount of protein, starch, oil, and other characteristics of food may be measured. In yet another environment, such blood constituents as glucose or cholesterol can be measured using such a device. In the area of pharmaceuticals, the drug composition of a sample can be determined and such features as the active zones of drugs can be measured. In the tobacco industry, such chemical characteristics as nicotine, tar and methol can be measured using such a device.
The second broad type of characteristics which can be measured using such a device are called physical parameters. Such physical parameters include physical characteristics such as viscosity of liquids. In addition, characteristics such as molecular weight or the multilayer thickness of various coatings can be measured.
The third major area which can be measured using the device described in the Landa patent are quality parameters such as degree of bake. For example, it may be necessary to determine when a cookie is properly cooked. One can use the spectral response from the cookie in the process of it being cooked to determine when to stop cooking.
Another area in which quality parameters can be measured involves, for example, adhesive strength. Another example of how the device disclosed in the Landa et al. patent may be used is in determining the taste of beers or wines. Since each of these products has a spectral signature, it may be possible to determine the quality of a wine by comparing the spectral signature of that wine with a known product or standard. For example, once the quality of a particular wine is known, it may be possible to take a spectral signature of that wine and determine what spectral characteristic or signature other wines must have in order to similarly have a good taste. Thereafter, other wines need not be taste-tested in order to determine that they are good wines. A spectral analysis only need be done and the signature be taken in order to determine such characteristic.
As stated above, the device described by the Landa patent is capable of determining the spectral characteristics of a number of different products in a number of different forms.
There are basically three modes of introducing and detecting light from a sample. The first way is through reflectance. In the reflectance mode, light is introduced into a sample via a probe. Light is then reflected back to the probe and the probe relays this information to the instrument which analyzes the light return. Generally, this type of instrument will have a bidirectional fiber arrangement which enables light to move in two directions through the probe.
The second mode of operation is transmittance. In this mode, a first probe introduces light through a sample and the second probe will receive that light which has been transmitted through the sample. In this mode, two probes are necessary.
The third mode of operation is the transflectance mode. This mode is similar to the reflectance mode in that a bidirectional fiber is generally used which both transmits and receives light from the sample. -n this mode, light is introduced to the sample. Light which is reflected from the sample is returned through the probe and transmitted back to the instrument for analysis. Light which transmits through the sample is reflected by a mirror back through the sample and again through the probe and on to the instrument for analysis.
For example, in order to obtain data for analysis, a probe may be inserted into a pipe to detect the constituents of a particular liquid product. If the probe is an optical rod surrounded by a sleeve, there can be a serious problem with introduction of liquid between the rod and the sleeve. This occurs if there are problems with the seal which is intended to prevent liquid from flowing between the rod and the sleeve. If such a problem occurs, the entire probe may need to be replaced. The reason that this is a serious problem is that each probe has particular characteristics. Therefore, by replacing one probe with another, the spectral signature which results may be altered as a function of the probe rather than a function of the material being analyzed.
Other probes in the art are made of a unitary structure. That is an optical bundle or the like may be surrounded by and epoxyed to a sleeve. Thus any failure in the optical bundle requires replacement of the entire probe. Since each probe has a distinct personality, the reliability of data is decreased. The above described unitary construction has an additional problem in that upon connecting the probe to a pipe or other body, a torque is normally required. If the probe is of unitary construction, any torque to the sleeve has a corresponding torque to the optical bundle. Such a torque can damage the probe thus causing additional delays and costs.
It is therefore an object of the invention to provide a probe which is modular.
It is a further object of the invention to provide a probe for introduction and receipt of light from a sample which is not sensitive to problems due to leaking.
It is yet a further object of the invention to provide a probe which may be used in solid samples such as cheese or meats or the like.
It is a further object of the invention to provide a probe which can be used in harsh environments, such as hydrofluoric acid, without adverse effects.
It is yet a further object of the invention to provide a probe in which the path length can be adjusted.
It is yet another object of the invention to provide a probe which does not necessitate the use of a separate and distinct mirror.
It is yet another object of the invention to provide a probe which has a bidirectional focusing capability to enable light passing through the probe to be focused onto optical fibers.
While the general concepts of the invention seeks to achieve the above stated objects, any individual embodiment may achieve these or other objects without varying from the invention.